A piece of metal weighs $45g$ in air and $25g$ in a liquid of density $1.5 \times {10^3}kg - {m^{ - 3}}$ kept at ${30^0}C$ . When the temperature of the liquid is raised to ${40^0}C$ , the metal piece is weighs $27g$. The density of liquid at ${40^0}C$, is $1.25 \times {10^3}kg - {m^{ - 3}}$. The coefficient of linear expansion of metal is